Microstructured waveguides and, in particular, photonic crystals, are known to provide wavelength-dependent filters, beam splitters, mirror components, right-angle waveguides and the like. In particular, photonic crystal materials modify the spontaneous emission rate of excited atoms, where the spontaneous emission is inhibited when the embedded atom has an emission frequency in the bandgap of the material.
Since conventional microstructured optical elements consist of structures which have dimensions on the order of several wavelengths along each of the two major axes, and are made with conventional microprocessing techniques, optical processing systems employing these elements can be extremely small. These relatively small devices thus find a variety of uses in high bit rate optical transmission systems. In order to reduce coupling losses in transmission systems employing such devices, various in-line (or “in-fiber”) devices have been developed. U.S. Pat. No. 6,075,915 issued to Koops et al. on Jun. 13, 2000 discloses the formation of a photonic crystal element directly in the path of light within an optical fiber. The Koops et al. photonic crystal element comprises an array of dielectric rods having one or more selective defects. Such a device is relatively difficult to form without adversely affecting the surrounding sections of optical fiber, or without introducing unwanted defects in the crystal area. Additionally, the number of rods and array size are naturally limited by the size of the fiber and the materials used to form the fiber.
Japanese Patent 2002-228808 issued to T. Mastoshi et al. on Aug. 14, 2002 discloses the function of “slicing” a photonic crystal fiber into a large number of sections, and using separate ones of these slices for the formation of the microstructured optical waveguides. Mastoshi et al. yield an improvement over the state of the art by following these fabrication steps (in sequence): (i) drawing the photonic fiber; (ii) polishing the fiber sides to make the rectangular cross-section; (iii) polishing the fiber ends to make the rectangular cross-section segments, and (iv) assembling the photonic circuit device by joining these segments together on a substrate. However, the actual technical implementations of the suggested procedure is rather difficult, as well as expensive and time consuming. For example, the surface quality of the sliced segments, as well as their interfaces, is extremely difficult to make sufficiently flat. The surface non-flatness will cause reflection and scattering of light and, as a result, will degrade the performance of the device. Also, for perfectly flat cuts, the light reflected from the sides of the slice will cause interference effect that will impact the transmission characteristics of the photonic device. Additionally, the process for assembling the fiber “slices” into larger photonic chips is not well-defined by Mastoshi et al and is not well-known in the art.
Thus, a need remains in the art for a relatively robust and cost-effective arrangement for utilizing complex microstructured elements with an optical transmission fiber.